That is why I've stuck with SRM's on my bikes. I know the data is good across the bikes.Alex Simmons/RST wrote:As to the statement "What matters is repeatability, not accuracy", well if you have true repeatability, then accuracy is simply matter of calibration. Something Stages does not permit you to do BTW (nor do many power meters, indeed the only ones that do are SRM and Quarq).
One also should consider the implications of longer term tracking and comparisons with historical data when one changes their power meter (unless you think your power meter will last forever or that its performance won't vary as it ages).
Power Meters (PowerTap P1 vs Pioneer versus Stages)
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby dalai47 » Sat Jan 14, 2017 2:33 pm
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby rockpaper » Sat Jan 14, 2017 4:11 pm
Thanks, scirocco, for the feedback on the stages. i had heard that, too, but thought it had improved as you say.
Interesting that ANT+ was chewing up batteries. usually, ANT+ is frugal...
nickobec, good point about a hire bike and compatibility, although all of the bikes I have hired overseas came with shimano kit. still, it is a good point and one that is swaying me...similarly to swap with my old bike on the trainer.
Alex, that was a very detailed post that was quite clear, and I particularly lied your reference to single-sided power meters as "good gateway drugs". I was heading toward the Pioneer or Powertap P1, anyway, and your post certainly points to the benefit of dual-sided power meters, although whether I will be good enough (in study and training) to take advantage of that is debatable...
Interesting that ANT+ was chewing up batteries. usually, ANT+ is frugal...
nickobec, good point about a hire bike and compatibility, although all of the bikes I have hired overseas came with shimano kit. still, it is a good point and one that is swaying me...similarly to swap with my old bike on the trainer.
Alex, that was a very detailed post that was quite clear, and I particularly lied your reference to single-sided power meters as "good gateway drugs". I was heading toward the Pioneer or Powertap P1, anyway, and your post certainly points to the benefit of dual-sided power meters, although whether I will be good enough (in study and training) to take advantage of that is debatable...
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby Alex Simmons/RST » Sat Jan 14, 2017 9:20 pm
I don't intend to dissuade people from the choices they make, rather just try to enlighten on the issues involved and to suggest they pause for a moment and think about why they are choosing to purchase a power meter and the applications they are hoping to use the data for. Once you understand that, then coupled with your budget the choice of meter becomes a bit easier.
But as a general principle, buy the meter that provides the best quality of data you can afford. The better the quality of data, the more applications of that data are possible - even if you may not yet appreciate what those applications are.
But as a general principle, buy the meter that provides the best quality of data you can afford. The better the quality of data, the more applications of that data are possible - even if you may not yet appreciate what those applications are.
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby rockpaper » Sun Jan 15, 2017 11:41 am
actually, i thought the commentary was excellent in your posts and all posts in the topic, in general. many of your comments are not discussed in reviews of power meters, although most power meter reviews are from commercial webpages, which means they can only comment so much about products.Alex Simmons/RST wrote:I don't intend to dissuade people from the choices they make, rather just try to enlighten on the issues involved and to suggest they pause for a moment and think about why they are choosing to purchase a power meter and the applications they are hoping to use the data for. Once you understand that, then coupled with your budget the choice of meter becomes a bit easier.
But as a general principle, buy the meter that provides the best quality of data you can afford. The better the quality of data, the more applications of that data are possible - even if you may not yet appreciate what those applications are.
it gave further fuel for thought.
thanks, everyone, for your assistance and comments.
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby rockpaper » Wed Jan 18, 2017 6:33 pm
Just a final note for the thread:
I have decided on pedals over cranks.
Now, just have to weigh up:
P1 pedals with look-style cleats (change to both pedals and stack height for me)
vs
garmin vector 2 with shimano conversion kit (same pedals)
really, it's how much i don't want to change pedal style and stack height (so choose garmin)
versus
the simple installation and movement between bikes of the P1 plus not having the garmin pods and teh not having to faff about with the torque wrench...
i think the P1 pedals are winning that argument.
cheers
rockpaper
I have decided on pedals over cranks.
Now, just have to weigh up:
P1 pedals with look-style cleats (change to both pedals and stack height for me)
vs
garmin vector 2 with shimano conversion kit (same pedals)
really, it's how much i don't want to change pedal style and stack height (so choose garmin)
versus
the simple installation and movement between bikes of the P1 plus not having the garmin pods and teh not having to faff about with the torque wrench...
i think the P1 pedals are winning that argument.
cheers
rockpaper
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby Alex Simmons/RST » Fri May 12, 2017 7:40 am
New study on power meter accuracy comparing 54 power meters from 9 manufacturers:
https://www.thieme-connect.de/products/ ... 043-102945
https://www.thieme-connect.de/products/ ... 043-102945
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby andrewjcw » Fri May 12, 2017 8:22 am
Ok... who has access?
https://www.strava.com/athletes/andrewjcw" onclick="window.open(this.href);return false;
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby Alex Simmons/RST » Fri May 12, 2017 12:17 pm
I've read it. A reasonable (but lab only) test method for assessing steady state aerobic level power outputs, which IMO is a relatively limited test of a power meter, but it is a valid way to provide absolute assessment of many different types of power meters for steady state aerobic power.
No mention if standard slope calibrations were performed on SRM and Quarq units prior to testing.
Not a valid test for high intensity or sprint power accuracy nor of performance in varying environmental conditions.
SRM and Powertap come up pretty well, Stages not so good but that's unsurprising given its a unilateral measurement.
No mention if standard slope calibrations were performed on SRM and Quarq units prior to testing.
Not a valid test for high intensity or sprint power accuracy nor of performance in varying environmental conditions.
SRM and Powertap come up pretty well, Stages not so good but that's unsurprising given its a unilateral measurement.
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby andrewjcw » Fri May 12, 2017 3:12 pm
No discussion into whether stages' lack of precision was caused by single sidedness as opposed to general inaccuracy? You'd think that would be one of the main practical investigations of such a study.
https://www.strava.com/athletes/andrewjcw" onclick="window.open(this.href);return false;
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Re: Power Meters (PowerTap P1 vs Pioneer versus Stages)
Postby Alex Simmons/RST » Fri May 12, 2017 5:27 pm
It was noted as an issue (see quote from study below where they address this point) but assessing why meters may or may not be accurate wasn't the purpose of the study, rather the study was to determine the level of power meter accuracy under the conditions tested and to use a methodology (negative gradient cycling treadmill and counter weights) which would provide an absolute accuracy benchmark (rather than simple relative tests of one meter v another).andrewjcw wrote:No discussion into whether stages' lack of precision was caused by single sidedness as opposed to general inaccuracy? You'd think that would be one of the main practical investigations of such a study.
For the rather low bar of steady state aerobic power accuracy, the fact that Stages is a unilateral meter is by its very nature going to result in lower precision. It's just a fact of life for such meters, no matter how well they measure one side, they will be both less accurate and less precise due to the normal and natural human variability in asymmetry of power output.
I think they are being rather kind. A meter's job is to be accurate and precise. If you design them such that they introduce an unknown and uncontrollable error, well you reap what you sow.The low CV of all power meters of 1.2 ± 0.9 % indicates high general precision of most power meters, but manufacturer-dependant differences exist. Power meters from SRM and PowerTap were more precise compared to devices from Stages.
This comparison, however, is not completely legitimate because the power meters from Stages calibrated in this study measured only torque in the left crank arm, with the assumption of right side being equal. Thus, the derived trueness and precision in the current study always depended on the power meter itself and the riding style of the cyclist (left-right balance). A varying left-right balance during the calibration would increase the variability of the measured power outputs and, therefore, lower the precision. Kirkland et al. [16] reported a contribution of 48.9 ± 3.6 % from the left leg in a group of 9 competitive cyclists for similar power outputs. The variability of 3.6 % illustrates how the accuracy of the Stages power meter could be strongly influenced by the cyclist himself, apart from technical measurement error.
Of course higher bars for power meter performance than this exist, e.g. precision and accuracy of high intensity cycling, sprint efforts and under variable crank velocity scenarios is where we see a much greater variability on the capability of meters, but which is actually quite hard to do relative to an absolute reference.
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